Öhlins Technology

Of course we get asked all the time… Why Öhlins? So we put together an ever evolving "Technical Guide" to help demonstrate what sets Öhlins apart. We will keep this thread updated as time goes on but you can also find this guide on our site as well: Öhlins Technical Guide

Öhlins has been an integrated part of the Motorsport industry for over 40 years. With its headquarters in Sweden, there are over 320 employees and a test center at the most demanding track in the world, the Nurburgring. Ohlins is the choice of Professional racers from Touring Cars to 24 Hours of LeMans and more. Even the new 2018 BMW M4 GT4 factory racecar is equiped with Öhlins dampers.

Did you know that all BMW EDC dampers from 2016 to current use Öhlins’ CES valves? To be clear the OEM dampers are not Öhlins, the OEM shock manufacturer sources these valves from Öhlins to use in the dampers.

Overview

WHAT SETS THE ROAD AND TRACK DAMPERS APART FROM THE COMPETITION?​

Dual Flow Valve Technology (DFV):
Traditionally dampers control the suspension with a piston (with shim stacks) and a bleed valve. The Ohlins damper introduces a third way with it’s Dual Flow Valve. Instead of relying on the main piston and/or bleed valve to control the suspension over bumps and potholes on the street (or curbs on the track) the dual flow valve takes over in this scenario. What this does is allows the bleed valve and piston with shim stack to focus on the racecar-like feel in the turns while bumps are absorbed by the DFV. You basically get the best of both worlds.

Inverted Strut Design (MacPherson Struts):
This is one of the most overlooked design features of a damper. A MacPherson strut suspension incorporates the damper as one of the control arms. Vertical and cornering loads put a bending load on the damper. A traditional upright damper will flex under load causing loss of camber and steering feel. In addition, the extra load on the piston shaft causes premature internal component wear leading to the common “blown shock.” Ohlins inverts the damper which removes the cornering load on the piston shaft and puts it on the external body of the damper. This is much more rigid which reduces camber loss, enhances steering feel, and increases longevity.

Temperature Compensation Bleed Valve:
It is well known that when engine oil gets hot the engine will make more power because there is less drag from the hotter oil. The same thing happens in your dampers, as the oil gets hot the damping force is reduced. What this means is that your car will handle differently throughout your trip around town or during an on track session. Ohlins has solved this problem with the temperature compensation bleed valve. As the damper heats up, the special valve will close just a little to keep the damping forces the same from cold to hot.

Gas Pressure Valve:
Gas pressure dampers need a way to insert the gas pressure once assembled. Most dampers use Shrader valves which are not reliable at all, we’ve seen them leak hours after initial assembly. Other manufacturers will tell you a shrader valve is superior but it simply is not. Ohlins uses self healing rubber diaphragms which lasts for years and potentially the life of the damper.

Vehicle Specific Valving:
Ohlins Road and Track kits are extensively developed to have the best damper valving for a specific spring rate. This method allows for very fine tune-ability of the balance of the car unlike a “catch all” damper. However, this does not mean you have to use the springs that come with the kit. You can use up to a 25% softer or stiffer spring without having to "revalve" the dampers. There is a lot of mis-information out there about "re-valved" shocks. We will expand on this more in detail below.

Dual Height Adjustment Method:
You have probably heard it 100s of times; if you lower your car too much you will run out of suspension travel and bottom out. Ohlins has the perfect solution to this problem, the Dual Height Adjustment. Now you can set your damper so that there is plenty of bump travel, then use the separate ride height adjuster to change the ride height of your car. Please note not all Ohlins suspension kits have this feature due to fitment constraints.

Longevity and Servicability:
The age old adage “you get what you pay for” couldn’t apply more with Ohlins… Between World Rally Championships, 24 hours of LeMans, and the harsh environment of Sweden, Öhlins is used to building components that survive the toughest environments in the world. The attention to quality machining and finishing processes, inverted strut design (for macPherson strut cars), and the diaphram type nitrogen valve are just a few examples of why these dampers are so robust.

The Details​

Dual Flow Valve Technology

A damper controls the upward movement (compression) and the downward movement (rebound) of the suspension. This movement is typically broken down into two levels, high speed and low speed. For example, hitting a bump on the street or the curbing on a track causes a high speed compression movement. Dropping down into a pot hole on the street or dropping off the end of track curbing causes a high speed rebound movement. Low speed movement of the suspension occurs when turning the vehicle. For example when turning to the right, the chassis will roll causing the left side suspension to compress slowly and the right side suspension to rebound slowly.

In an ideal world we want the damper to be stiff during low speed so that the car reacts quickly to steering inputs yet be soft when we hit pot holes or track curbs. This means that the wheel and tire can quickly and effectively resume their important position back on the ground, providing grip and traction. This is what the Dual Flow Valve technology accomplishes that sets Öhlins apart from its competitors.

Figure 1 &amp; 2 Below:
"1" is compression and "2" is rebound. At low speeds oil flows mostly through the shaft jet bleed (red arrow). At moderate speeds oil mostly flows through the piston ports (blue arrow).. At high speeds oil can escape through the DFV (green arrow) increasing comfort as well as grip.

FIGURE 3 Below:(Vehicle – no DFV) Without DFV the oil can not flow through the piston quickly enough on the rebound stroke after hitting a bump, so the tire is not able to stay in contact with the road.

FIGURE 4 Below:
(Vehicle – DFV technique) The DFV valve opens, letting the oil flow quicker through the piston on the rebound stroke after hitting a bump, enabling the tire to stay in contact with the road.

RIDE HEIGHT ADJUSTMENT

One the most unique features of the Öhlins Road and Track suspension kits is the dual height adjusters. Spring pre-load and ride height can be adjusted separately. On a traditional damper you can only adjust the ride height of the vehicle using the lower spring perch. The more you lower your vehicle, the less compression (bump) travel your suspension has. Lower the vehicle too much and you can bottom out the damper over even the slightest bump.

With the Öhlins Road and Track suspension kits you can lower your car and maintain sufficient bump travel at the same time! Image you have your ride height exactly where you want it but there is only 1" of compression travel. With a traditional damper your only option to get more compression travel is to spin the lower spring perch up. Now your ride height is not at your ideal location. With the Öhlins damper you would raise the lower spring perch up to get sufficient compression travel and then adjust the ride height adjuster to lower your car back down to the desired ride height. Problem solved!

*Please note: Not all applications have this dual height adjustment due to the limited diameter of the clamping ring on the front spindle.

INVERTED MACPHERSON STRUT DESIGN

There are two different types of damper (aka shock) designs within MacPherson strut suspensions (Figure A). There is an upright design (Figure B) and an inverted design (Figure C). The damper essentially acts like one of the control arms in the suspension system. As the suspension responds to vertical loads over bumps, the damper actually sees a bending load. It also sees bending loads from cornering. You want the damper to be as rigid as possible in bending for many reasons, but most importantly it provides better steering feel, ensures camber settings stay in spec under load, and greater longevity of the internal damper components.

A: MacPherson Strut

B: Upright Strut
An upright strut takes the bending load on the actual piston shaft itself. The piston shaft is supported by the upper guide bushing (green) and the piston (purple). The piston shaft is typically anywhere from .5" to .75" in diameter depending on the damper brand. This is not ideal for taking bending loads.

C: Inverted Strut
An inverted strut takes the bending load on the outside of the damper body. The damper body is supported by two guide bushings (yellow) in an outer tube whose sole purpose is to support bending loads. A typical inverted struts body is about 1.75" in diameter. This makes for a MUCH stiffer design in bending.

Why are OEM dampers upright if inverted is better? In a nutshell, they are cheaper to produce. One way to combat the bending load on the damper is with the spring. Have you ever noticed how the spring sits at an angle on your OEM strut? This is done to attempt to cancel out the bending load by lining up the centerline of the spring with the centerline of the wheel. When we "upgrade" to performance oriented suspension kits with adjustable height springs (coil overs) we loose the aid of an angled spring. Now the spring centerline is the same as the strut angle proving no offsetting force.

OTHER BENEFITS OF INVERTED STRUT

Guide Bushings and Seals:
Because the outer body of an inverted damper is taking the bending load, this means the piston shaft nor the piston itself have any side loading like an upright damper. This means the piston shaft guide bushing (green) lasts much longer before it needs replacing. The piston shaft also has seals that keep the pressurized oil from escaping the damper. The same applies to the seals, since there are no side loads from the piston shaft, the seals last much longer than an upright damper. The seals are also protected by the outer support tube which virtually eliminates the possibility of debris contamination.

Fluid Displacement and Gas Pressure Upright Strut:
On an upright damper, one way to increase bending rigidity is to increase the diameter of the piston shaft. Unfortunately, the larger the piston shaft, the less room there is for oil in the damper housing (white). Additionally, the larger the piston shaft displaces more fluid when compressed which in turn compresses the high pressure gas even more. In the diagram you will see where blue = uncompressed and Red = compressed too much. This increase in gas pressure results in extra unwanted forces and friction. Ideally you only want the gas pressure to be high enough to keep the fluid from cavitating and that is it.

Fluid Displacement and Gas Pressure Inverted Strut:
Since the piston shaft on an inverted strut sees no side loading, the piston shaft can be very small in diameter. This in turn allows for more fluid in the damper and prevents the gas pressure from becoming a factor at any point in the suspension travel. In the diagram you will see the where blue in both scenarios has a large enough volume to prevent high gas pressure.

TEMPERATURE COMPENSATION

Figure 5 Below:
As the piston moves within the damper, it generates friction – and therefore, heat. Although we can’t stop heat, we can deal with it, and this is yet another way that Öhlins differs from the competition. As the heat increases, the viscosity of the damper fluid can change, altering the car’s handling characteristics. Öhlins unique needle bleed valve expands with temperature, closing the gap that the fluid travels through, maintaining a consistent damping rate. The best thing of all? You won’t even notice! All you’ll feel is that the car responds consistently, lap after lap, turn after turn, allowing you to concentrate on braking points and apexes while the Öhlins technology takes care of the damping.

GAS PRESSURE VALVE

Mono tube dampers use gas pressure to keep the oil inside the shock from cavitating. This ensures the damping forces stay consistent in all scenarios, especially during high speed occurences. Traditionally, dampers use shrader valves to fill the damper with nitrogen which is very inconsistent and can leak over time. Ohlins uses a rubber diaphragm retain the nitrogen and is filled by a needle tool. Once the needle begins to be extracted, the diaphram seals itself not allowing any gas to escape.

Figure 1:
The needle valve is inserted in order to fill the gas chamber

Figure 2:
As soon as the needle starts to be extracted, the diaphragm seals itself, holding the exact pressure as seen on the gauge.

Figure 3:
Once the needle is fully removed the diaphragm stays sealed with no chance of leaking throughout the service life of the damper. A screw is then inserted to keep contaminates from wearing out the diaphragm.

Why not a Shrader Valve?:
A shrader valve has many intricate parts that can lead to failure. As gas pressure is added, the valve is opened (Figure 4). Once the valve is closed (Figure 5), it relies on a perfectly clean seal (Red Arrow) to retain the gas pressure. The slightest contaminate or degradation in the seal can cause the gas pressure to escape. A slightly bent plunger can also lead to a bad seal.

Figure 4:Figure 5:

Ohlins’ Development Philosophy and Procedure​

Despite what other suspension manufacturers may tell you, comfort is king, even when you are trying to set-up a competition machine. Ohlins’ vast experience on events like the World Rally Championship, Nürburgring and Isle of Man TT races has shown them that the fastest drivers and riders are those that aren’t being shaken to bits. The ‘science of compliance’ is a hugely important part of their design work.

Development is a step by step process which starts with their test drivers driving the car on public roads just outside Stockholm, and on their racetrack to set a benchmark. The goal is to collect enough data about the current setup from driving on the racetrack and public roads.

What data is of their interest? They measure all specific parameters of the suspension, such as the motion ratios, ride-height, roll-centre etc. They are also performing a corner-weight of the car. This data is vital for the next stages of Their development process.

With their purpose-built software, they develop an initial setting with feedback from their test drivers. From the first setting, they can begin to build an early proposal damper-setting and spring stiffness. When the computer-based model is developed, it’s time to build and fit the first Öhlins Road &amp; Track prototypes to the car.

With the prototypes fitted to the car their technicians and engineers hand over the car to their test drivers again. A first shakedown performed on the racetrack to make sure that we have a safe product.

After the shakedown, they begin to stress the dampers with high-speed maneuvers, and they also find out if the computer modelling of the damper-settings and spring stiffness are correct. Though the dampers are primarily intended to be used on the racetrack, their engineers and test drivers spend much time to find a comfort-setting for road use. The Road &amp; Track dampers from Öhlins are often more comfortable than the standard suspension.

The process to find the optimum track setting and road setting may take some time. Öhlins is a perfectionist company, and that is clear in their development process. If their test drivers and engineers are not pleased with a particular setting, they change it until they are sure that this is the best possible match between Road &amp; Track.

The final step in the Öhlins Road &amp; Track Development Process is to finalize and prepare the dampers for production. All documentation and prototypes used during the development phases are saved for regulatory compliance to meet legal demands.

The Öhlins Road &amp; Track Development Process is executed for every single car model. Every setting is tailor-made and evaluated thoroughly before being transferred to series production. Their test drivers put in thousands of test kilometers to ensure the perfect handling combined with comfort. They develop their dampers after careful calculations to secure a high-quality product, which is safe to use when driving on the absolute edge. All in all, Öhlins Road &amp; Track group takes care of testing and development to find the optimum performance so you can focus on driving your car with a smile! Drive safe!